(1) Field of the Invention
This invention relates to a tire warm-up wrap, i.e., a wrapping device which is used for pre-heating tires of motor racing cars and motor cycles immediately before the start of a race.
(2) Description of the Related Art
Immediately after the start of a race, the temperature and pressure of motor racing tires are not yet at their normal track levels, and therefore, their road-holding is inferior and the acceleration force is not full. To obviate this defect, motor racing tires are usually pre-heated by a warm-up wrap immediately before the start of a race.
A typical example of conventional warm-up wrap comprises a sheet-form heat-generator made of superposed plastic films or fabrics which are stitched together with a plurality of long and parallel seam lines to form parallel hollow spaces, into which electric heating elements such as nichrome wires, chromium-iron wires and copper-nickel wires are inserted so as to constitute a series resistance circuit. The warm-up wrap is wrapped around a tire so that the tread thereof is entirely covered by the wrap and an electric current is applied thereto to heat the tread.
The above-mentioned warm-up wrap has problems such that uniform heating is difficult to attain, and the wrap has a poor flexural fatigue resistance and flexibility and hence wire breakage occurs due to repeated flexing during the use.
A proposal has been made wherein an electric-heating element of a thread form comprised of a thread coated with an electrically conductive layer composed of a synthetic resin having been dispersed therein particles of carbon or a metal (Japanese Unexamined Patent Publication No. 62-100771). This thread-form electric heating element has problems such that the electric resistance is large and the quantity of electricity is minor, and thus, it is difficult to heat a tire of a large size to the desired temperature within a reasonably short period of time, and also difficult to bend the wrap at a sharp angle.